Parasitic nematodes represent a potential threat to the health and growth of warm-blooded animals. In some cases, infestation can become so extreme that the animals succumb to the parasites. The parasites spend at least one stage of their life cycle in the animal's intestinal tract, and rob the host animal of nutrients which would otherwise contribute to its growth.
Control and elimination of such intestinal parasites is complicated by their location in the alimentary system of the host animal. Any compound which is to be used must be selectively toxic to the parasitic worms without having an adverse effect on the host animal, or without contaminating food products obtained from the host animal (meat, dairy products).
Oral administration of the anthelmintic compound is preferred, so that the compound enters the alimentary system of the animal directly, and is released in effective amounts at the site of the parasites in the intestine. The compound should pass through the first portion of host animal's alimentary system without loss of efficacy so that it can be released at full potency at the locus of infestation.
A number of anthelmintic compounds have been described. U.S. Pat. No. 3,574,845 is directed to the use of esters of benzimidazolyl carbamic acids and their thio analogs which are said to be effective against mouse pinworms, whipworms in dogs, parasitic gastroenteritis in sheep, verminous pneumonia in pigs and various helminthic parasites which attack cattle.
U.S. Pat. No. 3,314,849 describes the use of alphahaloacetamides having long aliphatic chains substituted on the amide nitrogen atoms as anthelmintic compounds. These compounds were specifically described as being effective against Turbatrix aceti, Strongyloides ratti, Aspicularis tetraptera, and Syphacia obvelata.
Some quinoxaline compounds are already known for other biological uses. For example, U.S. Pat. No. 3,433,871 discloses the Schiff bases of 2-formylquinoxaline-1,4-dioxides are useful as growth promoters, and also useful as systemic and non-systemic infection control agents in animals. More particularly, the subject compounds are used to control chronic respiratory disease in poultry, infectious sinusitis in turkeys, urinary tract and systemic and non-systemic infections in animals. The above patent does not suggest the use of the named compounds as anthelmintics, and it is directed to amino derivatives of 2-lower alka-noyl quinoxaline-1,4-dioxide.
Quinoxalinyl-oxazolidines and oxazines are described in U.S. Pat. No. 3,647,790 and are said to be useful as nervous system depressants to induce a calming effect in animals. No other uses are disclosed.
Certain 2-imidazoline substituted quinoxaline-1,4-dioxides are disclosed in U.S. Pat. No. 3,870,718. The use of these compositions as antibacterial agents is described. However, there is no mention of possible anthelmintic use.
British Pat. No. 1,223,720 describes certain quinoxaline derivatives. However, no mention is made of possible anthelmintic use.
U.S. Pat. No. 3,371,090 discloses the same compositions described in U.S. Pat. No. 3,433,871. The same uses are also described, plus use as a growth promoter and for improving feed efficiency in poultry, sheep, steers, goats, dogs and mink. No mention of possible use as an anthelmintic is made.
Substituted quinoxalines are disclosed in U.S. Pat. No. 4,076,815 as being useful in treating cholera in humans, and for sterilizing cholera (vibrio organism) infected water. The compounds described include pyrimidinyl substituents. The only use suggested for these compounds is for combatting cholera.